Greases thickened with aromatic polyamide-imides and poly-4-phthalimide

ABSTRACT

Lubricating oils thickened to greases with aromatic polyamideimides and poly-4-phthalimide.

United States Patent 1 1 Dobry 1 Nov. 20, 1973 54] GREASES THICKENED WITH AROMATIC 3,025,241 3/1962 Dreher et a] 252/515 A POLYAMIDE-IMIDES AND :32? POLYAJHTHALIMIDE 3:661:779 5/1972 Stanton 252/515 A Inventor:

US. Cl 252/51.5 A

Int. Cl. C10m 5/20, ClOm 7/34 Field of Search 252/515 A References Cited UNITED STATES PATENTS 6/1963 Dreher et a1 252/515 A Primary ExaminerDaniel E. Wyman Assistant Examiner-I. Vaughn Att0rneyArthur G. Gilkes et al.

[5 7] ABSTRACT Lubricating oils thickened to greases with aromatic polyamideimides and p0ly-4-phthalimide.

8 Claims, No Drawings GREASES TI-IICKENED WITH AROMATIC POLYAMIDE-IMIDES AND POLY-4-PHTHALIMIDE The invention herein described was made in the course of or under a contract with the Department of the Air Force.

FIELD OF THE INVENTION This invention relates to lubricating grease compositions in which the thickening agent is a polymeric material.

SUMMARY OF THE INVENTION The lubricating greases of this invention comprise a lubricating fluid and a thermally stable polyamideimide or polyimide.

The present invention is based on the discovery that the herein-described finely-divided solid polymeric material, which is chemically unreactive with and insoluble in the lubricating fluid, can be dispersed in the lubricating fluid to form a homogeneous fluid/thickener system that is suitable for use as a lubricant grease.

Polyamides-imides and polyimides are well-known classes of thermally stable polymers having many uses, especially in fiber, film, coating and plastics industries. The present invention is limited to the use of these known classes of polymeric materials as grease-forming thickeners in lubricating fluids. Accordingly, the polymers per se and their preparation do not constitute any part of this invention.

The chemical composition and structure of these polymeric materials are not critical with respect to the present invention. The polymers may be formed from any combination of aliphatic, aromatic or heterocyclic monomers known in the art that will provide amido and imido linkages in the polyamide-imide or polyimide polymers; provided, however, the polymer contains at least 5 percent imido linkages in its chain. The only other limitation presently known is that the polymer be thermally stable at the temperature of intended use of the grease. Accordingly, the grease manufacturer has a broad spectrum of polymeric materials from which to choose.

The polymeric thickener is used in an amount sufficient to thicken the lubricating fluid and form the grease having the desired consistency or penetration.

.The amountis genrmbetween abouti and about 50 weight percent, usually between about 8 and about 30 weight percent, of the total composition.

The lubricating fluid component of the greases of this invention can be any normally liquid lubricating oil or fluid of natural or synthetic origin that is normally used in lubricant grease compositions. Illustrative of such oils are the conventional mineral lubricating oils and synthetic lubricating fluids or oils, such as silicone oils, fluorosilicone oils, polyether fluids, polyester fluids, polyfluoro fluids, etc., having viscosities within lubricating oil viscosity range.

The lubricant grease compositions of the present invention can contain, if desired, lubricant additives well known to the art without departing from the scope of the invention. For example, such greases can contain corrosion and/or rust inhibitors, E.P. agents, antioxidants, metal deactivators, stabilizers, anti-wear agents, and the like. The use of such additives and the amounts thereof depend upon the severity of the conditions to which the grease may be subjected.

The polymeric thickeners of this invention are finelydivided thermally stable solid materials which are inert and insoluble in the lubricating fluid. The term thermally stable means that the thickener does not melt or soften at grease operating temperatures.

The grease compositions are prepared by simply dispersing the solid polymeric thickener, in finely divided particulate form, such as a powder, in the fluid and then milling the dispersion mixture to the desired grease consistency. Any method of mixing that imparts shearing action may be used. Preferably, the conventional grease roll mill is used to form a grease having a stable consistency or penetration. The particle size of the thickener is not critical, but the particles should be as small as possible, since it is well known that the stability of the grease is dependent upon the particle size of the solid thickener. Inasmuch as the polymeric thickener is inert and insoluble in the lubricating fluid, it is to be understood that a plurality of passes through a roll mill and adjustment of fluid content are required to obtain homogenity of the solid thickener/fluid system and effect a stable consistency in the grease.

' The CRC L-35 bearing performance test was used to determine the performance of the exemplary grease formulations of this invention as bearing lubricants at elevated operating temperatures. At temperatures below 566 E, the size 234 test bearings were run in high speed test spindles at lOIIOUrpm in air, with a 5 pound radial load and a 5 pound axial load on the bearing,for 20 hours out of each 24 hour period until failure. In tests at or above 500 F, the test bearings, under a 50 pound radial load and a 25 pound axial load, were run continuously at the test temperature,

until failure. All tests at atmospheric pressure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyamide-imides and polyimides used as thickeners in the exemplary grease formulations of this invention are:

Polymer A: poly 4-phthalimide. The homopolymer derived by heating the dimethyl ester of 4- aminophthalic acid.

Polymer B: a polyimide of pyromellitic dianhydride and oxy-bis-aniline available commercially in solution form as a wire enamel under the trade name Pyre- ML. The commercial solution was diluted with N,N- dimethyl acetamide and precipitated in water and thoroughly washed with water. The powder solids were dried at a pressure o f a bout l5 Torr for f t hours a t SU C, followed by 2 hours at 200C. The dried powder was then used as the thickener.

Polymer C: a polytn'mellitamide-imide of the 4-acid chloride of trimellitic anhydride and methylenebis-aniline.

Polymer D: a polytrimellitamide-imide of the 4-acid chloride of trimellitic anhydride and p,p'-oxy-bisaniline. I

Polymer E: a polytrimellitarnide-imide of t h Z-acid chloride of trimellitic anhydride and m-phenylene diamine.

Polymefi iapoly tfiriiellifa mide iinidof the lacid chloride of trimellitic anhydride and a mixture of 76 11 161 percent p,p ox' bis-arnnfia and 3ll mol percent m-phenylene diamine. The polymers C-F are the imidized polymeric solids of the amic acid reaction product obtained from the recited reactants. Drying of the intermediate an ic acid solids to effect imi d i z ation was at a pressure of Torr for 2 hours at 200C. Preparation of the solid amic acid products is fully described in US. Pat. No. 3,573,260 which relates to preparation of solid molding powders from polytrimellitamide-imides. The amic acid polymeric solids referred to herein are the starting materials for the molding powders of aforesaid U. S. Pat. No.

3,573,260 which paten t is incorporated by reference herein.

EYAMPLEY 7 In this example the Dow-Corning silicone polymer lubricating fluid F 6-7039 was thickened with thepolymers described above. The lubricant grease obtained was then tested as a bearing lubricant. The respective g'feiis formulatio risjhaviiig XSTWFD TZQ quartercone penetrations of about 300, and the bearing test results are set forth in Table I:

The liquid lubricating fluid used in forming the greases of t his example wasKrytoY l43ADTaperfluorinated polyether oil derived from hexafluoropropylene oxide. Polymers A-F were used as the thickening agent for this fluid. The greases, having quartercone penetrations of about 300, so formed and the bearing test results are set forth in Table II:

TABLE II Thickener Bearing Test Life Polymer (Hours) at 550F. A 307 B 10 7l 17.6 399 C l7.l I22 I89 416 D 8.1 427 E 12.5 507 F 33 132' EXAMPLE 3 A grease containing 38 weight percent Polymer A as thickener for Dow-Coming silicone polymer lubricating fluid DC-510 was tested in the bearing test and ran for 1,584 hours at 450 F. The same grease tested at 500 F ran for 288 hours.

A hydrorefined petrolem lubricating oil of SAE-40 grade was thickened with 40 weight percent of Polymer A. This grease in duplicate runs ran for 119 and 200 hours at 350 F.

The synthetic lubricating fluids used in the foregoing examples are all commercially available products and are well known in the art.

I claim:

1. The grease composition comprising a lubricating fluid and an amount of a polymeric thickener sufficient to thicken the fluid to grease consistency, said thickener consisting essentially of a member selected from the group consisting of a thermally stable aromatic polyamid imide and thermally stable phthalimide.

2. The composition of claim 1 wherein the amount of said thickener is from about 5 to about 50 weight percent.

3. The composition of claim 1 wherein said thickener is poly-4-phthalimide.

4. The composition of claim 1 wherein said polyamide-imide is a polytrimellitamide-imide polymer obtainedTnSinthe amic acid reacfiafiqsraauct of"4-acid chloride of trimellitic anhydride and an aromatic diamine.

5. The composition of claim 4 wherein said diamine is methylene-bis-aniline.

6. The composition of claim 4 wherein said diamine is meta-phenylenediamine.

7. The composition of claim 4 wherein said diamine is p,p-oxy-bis-aniline.

8. The composition of claim 4 wherein said diamine is a miiiture of mol percent p,p"- oky bis-aniline and 30 mol percent meta-phenylenediamine.

poly-4- 

2. The composition of claim 1 wherein the amount of said thickener is from about 5 to about 50 weight percent.
 3. The composition of claim 1 wherein said thickener is poly-4-phthalimide.
 4. The composition of claim 1 wherein said polyamide-imide is a polytrimellitamide-imide polymer obtained from the amic acid reaction product of 4-acid chloride of trimellitic anhydride and an aromatic diamine.
 5. The composition of claim 4 wherein said diamine is methylene-bis-aniline.
 6. The composition of claim 4 wherein said diamine is meta-phenylenediamine.
 7. The composition of claim 4 wherein said diamine is p,p''-oxy-bis-aniline.
 8. The composition of claim 4 wherein said diamine is a mixture of 70 mol percent p,p''-oxy-bis-aniline and 30 mol percent meta-phenylenediamine. 